Fuel oil control system



March 1952 c. D. Ma cRAcKEN ETAL FUEL OIL CONTROL SYSTEM Filed Jan'. 15, 1949 R m v. 2 WWW E 1 mm in; T 4

\ war/4 Patented Mar. 25, 1952 UNITED STATES PATENT OFFICE FUEL OIL CONTROL SYSTEM of New York Application January 13, 1949, Serial No. 70,773

3 Claims.

gallons per hour which is sufficient for heating purposes in most house-heating and certain other systems. The term fuel oil as hereinafter used is intended to include any liquid fuel.

Mechanical atomizers of the return-flow type are characterized by a central whirling chamber to which the fuel-oil is supplied, at substantially constant pressure, through tangential passages, thereby imparting whirling motion to the oil in said chamber some of which is discharged in a spray through a small orifice and some of which leaves the whirling chamber through an orifice or orifices communicating with a pipe through which the oil returns to the supply source. The quantity of fuel-oil emitted from an atomizer of that type in the form of a spray may be controlled by regulating the flow of oil through the return pipe by providing therein a valve which is manually or otherwise operated. These returnfiow type atomizers are particularly useful at low fuel-oil delivery rates, because their larger total fuel-oil fiow requires greater internal dimensions and gives a cooling and scouring action, all of which greatly reduces the tendency to plug-up with dirt or fuel-oil residue.

So long as the temperature ofthe oil passing through the atomizer remains substantially constant, the viscosity of the oil is substantially constant, and the quantity of oil supplied from the atomizer in the form of a spray for combustion purposes will not vary substantially if the pressure in the return pipe is held constant. However, in many heating systems, the temperature of the fuel-oil in the supply tank may vary considerably, particularly when the tank is located out-ofdoors; and we have found that such variations in the temperature of the oil which is supplied to the atomizer may cause considerable variation in the quantity of oil supplied as a spray for combustion purposes by theatomizer. Such variations are due to changes in the viscosity of the fuel-oil which has a lower viscosity at high temperatures than at low temperatures. It is incorrect, however, to assume that the quantity of fueloil emitted by an atomizer of the type mentioned is greater when the oil has a high temperature and low viscosity, than when it has a low temperature and high viscosity. In fact, the contrary is true; and it is our belief that this is due to the fact that, when the temperature of the oil is high and its viscosity is low, more rapid whirling of the oil within the atomizer and decreased resistance in the return passage, which is larger than the spray orifice, result in a decrease of the total amount of oil which flows out of the spray orifice.

Normally, there may be a rise of perhaps 20 F. in the temperature of the fuel-oil during its passage from the supply tank to and through the atomizer. If the tank is located out-of-doors and the temperature of the oil in it is 0 F; the temperature of the oil in the atomizer may be about 20 F., but, if the temperature of the oil in the tank is F., the temperature of the oil in the atomizer may be about F. Therefore, when the fuel-oil in the supply tank has such widely varying temperatures, there is a considerable difference in the viscosity of the oil in the whirling chamber in the atomizer; and, due to this fact, there may be a considerable difference in the amount of oil which is emitted from the atomizer as a spray for combustion purposes.

An important object of the present invention is to maintain substantially constant, thequantity of oil emitted in a spray by an atomizer'in a system of the kind above mentioned, notwithstanding variations of the temperature of the oil. Another object of the invention is to prevent bleeding of the oil from the return-pipe back into the atomizer and out of the spray opening therein, when the system is shut down by cutting off the supply of oil to the atomizer.

According to the present invention, these objects are attained by providing in the return line from the atomizer a pressure regulating device which automatically responds to variations'in the temperature of the oil passing through said device, and' exerts on the oil flowing in the return pipe a throttling effect which is greater'at high temperatures of the oil than at low temperatures thereof, and which, upon shutting off the oil supply, prevents any back fiow of fuel to the atommen The novel pressure regulating device described herein is claimed in a divisional application, Ser. No. 195,202, filed November 13, 1950, this application being directed to the novel combination constituting the system as a whole.

The invention will be understood from the following description taken in connection with the accompanying drawing in which Fig. 1 is a diagrammatic representation of fuel-oil control system embodying the invention; Fig. 2 is a sectional elevation of the novel pressure regulator employed in that system; and Fig. 3 is a sectional elevation, on an enlarged scale, showing the construction of the temperature responsive element of the pressure regulator.

Referring to Fig. 1 of the drawing, a mechanical fuel-oil atomizer 4 of the return-flow type is shown as supplied with fuel-oil from an oil tank 6 at a substantially constant pressure by an oil pump 8; and the return-flow outlet of the atomizer t is connected through a pressure regulator III (of the type illustrated in Fig. 2 and hereinafter described) to the oil tank 6. As will hereafter appear, the pressure regulator l0, through which flows the oil returning from the atomizer 4, is characterized by the fact that it contains an element responding to the temperature of the oil and functioning to increase and decrease the throttling effect of the regulator on the oil flowing through it, with the rise and fall of the temperature of the oil. That is, after the pressure regulator III has been set so as to exert a throttling efiect on the returning oil such that the atomizer will spray fuel-oil at the desired rate, the pressure regulator will continue to function in response to varying temperatures of the oil so that the throttling effect of the regulator will maintain substantially constant the quantity of oil sprayed by the atomizer.

Referring now to Fig. 2, in which the construction of the pressure regulator I0 is illustrated, it will be evident that the regulator has a casing made in two parts l2 and I4 having cooperating flanges which are bolted together by the bolts 15. A flexible circular diaphragm iii, of Neoprene or any other suitable material, the edge of which is clamped between the flanges of the casing parts l2 and I4, is thus mounted within the casing and serves as a movable valve member. It will be seen that the casing part M is provided with a chamber l8 having an oil-flow opening 20 and surrounded by a circular lip 22 which cooperates with the diaphragm l6 and serves as a valve seat. The casing part I4 is also provided with a circular trough 23 located outside of and concentric with said lip 22; and this trough is provided with an oil-flow opening 24. Cooperating with the diaphragm I6, is a backing member consisting of a circular plate 26 having a hub 21 provided with a central hole through which is threaded a bolt 28 having a nut 30 cooperating therewith and with the hub 2! of the plate 26. It will be obvious from the drawing that the plate 26 forming part of the backing member cooperates with the upper side of the diaphragm l6, and that said plate 26 extends outwardly to the neighborhood of the lip 22 and preferably to approximately the outer edge of said lip. Thus the plate 26 confines the upward flexing of the diaphragm IE to that portion of the latter which is between the outer edge of the plate 26 and the casing flanges between which the edge of the diaphragm I6 is clamped. In Fig. 2, the space shown between the diaphragm l6 and the lip 22, and the flexing of the diaphragm i6 are both exaggerated, in order to aid in understanding that in the functioning of the regulator the oil flows from the chamber l8 over the lip 22 into the trough 23. Since diaphragm I6 is fastened to plate 26 only at the center, nothing holds the diaphragm off its seat 22 except the pressure of the oil flowing between the seat and the adjacent portion of the diaphragm, and when there is no pressure or the slightest negative pressure the diaphragm immediately seals against its seat. Since there is only a thin film of oil separating them, practically no oil is displaced when such sealing occurs. Located within the casing section I2 is a coiled spring 32 which at its lower end cooperates with the plate 26 of the backing member and at its upper end with 'a disc 34 engaged by a screw 36 threaded through a hole in the top of the casing member [2. It will be understood that the screw 36 may be adjusted so as to cause the spring 32 to exert any desired pressure upon the backing member which cooperates with the diaphragm [6.

Located within the chamber 18 in the casing member I4, is a temperature responsive means which is illustrated on an enlarged scale in Fig. 3. This temperature responsive means consists of two bi-metal discs spaced apart and secured to one another at their edges by a ring 40. As is best shown in Fig. 3, each of the discs of the temperature responsive device is composed of two layers 42-43 and 44-45 of metal welded together, said layers having different coefficients of expansion under variations in temperature. The layers 42 and 44 having the lower coefficients of expansion are located on the outside, and the layers '43 and 45 having higher coefficients of expansion are located on the inside of the temperature responsive means. Said discs (which are flat at room temperature with no compression but which are shown in Figs. 2 and 3 under initial compression from the force of the spring 32) buckle toward one another at higher temperatures and away from one another at lower temperatures. As will be apparent from Fig. 2, the casing member [4 is provided in the bottom of the chamber l8 with an abutment 46 having an upwardly extending central portion 48; and the discs of the temperature responsive means just described are provided at their centers with openings adapted to receive the upwardly extending portion 48 of the abutment 46. In this way, the temperature responsive means is centered in the chamber I8. It will also be evident that the bolt 28 is provided at its lower end with a cup-shaped head 50 the edges of which are adapted to cooperate with the temperature responsive means, as shown in Fig. 2. Thus the abutment and bolt head 50 limit the compression of the temperature responsive means under the force of the spring 32 so that the disc will not be overstressed. The inlet opening 20 in the casing member l4 may be provided with a check valve 52, as shown in Fig. 2, but this check valve may be omitted if desired.

The mode of operation of the pressure regulator will be understood with the aid of Fig. 2. The oil, returning from the atomizer 4 through the opening 20, fills the chamber I8 and flows over the lip 22 into the trough 23 and from that trough flows out through the opening 24 and on to the fuel-oil tank 6 or instead to the intake side of the pump if desired. As long as the oil remains at the temperature it had when the screw 36 was set, cooperation of the diaphragm It; with the lip 22 will exert on the oil a constant throttling effect. Upon a rise in the temperature of the oil flowing through the chamber 18 and bathing the temperature responsive element, the discs in the temperature responsive element will flex toward one another, thereby increasing the net effective pressure exerted by the spring 32 upon the backing member and the diaphragm 16 thus increasing the throttling effect on the oil flowing between the diaphragm l6 and the lip 22. The action of the thermal responsive element is not actually to raise or lower the diaphragm from its seat but to counterbalance the spring pressure on the diaphragm, to a greater or less extent, which opposes the pressure of the fuel in the return flow pipe. If, however, the temperature of the oil decreases, the discs of the temperature responsive element will flex away from one another, thus decreasing the net effective pressure exerted on the backing member by the spring 32 and decreasing the throttling effect on the oil flowing between the diaphragm l6 and the lip 22. In this way, the pressure of the oil in the return passage of the atomizer 4 is automatically increased and decreased with the rising and falling of the temperature of the oil, that is, with the decreasing and increasing of the viscosity of the oil, with the result that the atomizer will spray oil at substantially a constant rate, even though the viscosity of the oil passing through the atomizer varies considerably. As has been stated, Fig.2 represents in exaggerated form the space between the diaphragm l6 and the lip 22; and this space is in fact very small at all times, because the rate of oil flow between the diaphragm i6 and the lip 22 is very low during the functioning of the pressure regulator in combination with a mechanical atomizer of the returnfiow type designed to supply a fuel-oil spray at the low rates above mentioned. Virtually, the oil squeezes through between the seat 22 and the diaphragm I5 in a film. of almost unmeasurable thinness against the net effective pressure of the spring.

When a fuel-oil control system of the kind illustrated in Fig. 1 is shut down by cutting off the supply of oil to the spray nozzle 4, it is important that no oil be allowed to bleed" back into the atomizer 4 from the return pipe. The pressure regulator shown in Fig. 2 prevents such back-flow into the oil atomizer, due to the fact that when the supply of oil to the atomizer is cut off the pressure of the oil in the return-flow pipe drops, and the outer portion of the diaphragm l6 instantly flexes into contact with the lip 22, thereby preventing back-flow toward the atomizer of the fuel-oil trapped in the return pipe and in the pressure regulator. Because the flexing of the diaphragm l6 displaces only a minute quantity of oil from between the diaphragm I6 and the lip 22, the result is that substantially no back-flow of oil to the atomizer occurs. The check valve 52 assists in preventing such backflow of oil but, as has been mentioned, this check valve is unnecessary under most conditions of operation because in the absence of a defect of the diaphragm it forms a complete seal by itself.

It will be understood that, when used with different oils having varying viscosities and with L different types of return-flow nozzles having varying pressure-flow characteristics, the temperature responsive means will have to be changed accordingly. This is best done by varying the thickness of the bi-metallic discs which is normally about .025 to .030 of an inch. Also, if less temperature compensation is required, the thickness of the discs should be less and viceversa. In this disclosure two bi-metallic elements have been used in order to reduce the spring rate, that is, the rate of change of force exerted by the bi-metallic elements as they are further compressed. This is desirable in order to reduce sensitivity to dimensional tolerances. It should be understood that this effect can be accomplished in other ways or may not be necessary, and that a single bi-metallic element with corresponding changes in cooperating parts can be used.

What is claimed is:

1. A system for supplying to a burner a constant atomized flow of liquid fuel subject to variations in viscosity due to changes in its temperature, said system comprising, a fuel atomizer of the return-flow type,-means for supplying fuel to said atomizer under pressure, a return flow pipe for conducting unatomized fuel away from said atomizer, and a pressure actuated throttling device in said pipe, said device including temperature responsive means bathed by the fuel flowing through said device and arranged to increase the throttling effect of said device upon ,an increase in fuel temperature and to decrease the throttling efiect of said device upon a decrease in fuel temperature, whereby the flow of atomized fuel from said nozzle is maintained substantially constant notwithstanding variations in its temperature.

2. A system for supplying to a burner a constant atomized flow of liquid fuel subject to variations in viscosity due to changes in its temperature comprising, a fuel atomizer of the returnflow type, means for supplying fuel to said atomizer under pressure, a return flow pipe for conducting unatomized fuel away from said atomizer, and a pressure actuated throttling device in said pipe, a chamber in said device, said device including temperature responsive means in said chamber bathed by the fuel flowing through said device and arranged to increase the throttling effect of said device upon an increase in fuel temperature and to decrease the throttling effect of said device upon a decrease in fuel temperature, and means preventing flow from said chamber back to said atomizer whereby the flow of atomized fuel is maintained substantially constant notwithstanding variations in its temperature.

3. A system for supplying to a burner a constant atomized flow of liquid fuel subject to variations in viscosity due to changes in its temperature, said system comprising a fuel atomizer of the return-flow type, means for supplying fuel to said atomizer under pressure, a return flow pipe for conducting unatomized fuel away from said atomizer, and a pressure actuated throttling device in said pipe, said device including a temperature responsive bimetallic element bathed by the fuel flowing through said device and arranged to increase the pressure required to actuate said device upon an increase in fuel temperature and to decrease the pressure required to actuate said device upon a decrease in fuel temperature, whereby the flow of atomized fuel from said nozzle is maintained substantially constant notwithstanding variations in its temperature.

CALVIN D. MACCRACKEN. CHARLES W. WOOD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 853,541 Eddy May 14, 1907 1,220,985 Harter e Mar. 27, 1917 1,656,392 Russel et al Jan. 17, 1928 1,824,952 Graham et a1 Sept. 29, 1931 1,854,402 Goosmann Apr. 19, 1932 1,871,287 Whitaker Aug. 9, 1932 1,894,842 Appelberg Jan. 17, 1933 1,941,023 Smith Dec. 26, 1933 1,966,098 Kuenhold July 10, 1934 1,972,908 Shaw Sept. 11, 1934 2,037,994 Neubauer Apr. 21, 1936 2,115,665 Florez et a1. l Apr. 26, 1938 2,139,050 Vickers Dec. 6, 1938 2,286,581: Scott June 16, 1942 2,451,707 Armstrong Oct. 19, 1948 2,471,541 Plass May 31, 1949 OTHER REFERENCES ASME Transactions, vol. 61 of 1939, pages 373- 381. 

